Flat coreless vibrator motor having no output shaft

ABSTRACT

One end of a shaft is fixed to a first portion of a housing. An eccentric rotor is located in the housing rotatably on the shaft. The other end of the shaft is fitted into a concave portion on a second portion of the housing, so the rotor may be assembled in the housing in a simple manner and radial movement of the shaft can be prevented without enlarging the fixing portion of the shaft. Even if the diameter of the shaft is small, the shaft can withstand an impact resulting from dropping of the motor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flat coreless vibrator motor havingno output shaft, which motor is suitable used as a silent informationsource for a small-sized radio calling device (or a pager) or as avibration source for a massager and, more particularly, to an improvedfixed shaft type structure of the coreless vibrator motor provided witha thin fixed shaft.

2. Description of the Related Art

Conventionally, a flat vibrator motor without an output shaft has beenknown, especially as a flat coreless motor disclosed in the U.S. Pat.No. 5,036,239. As shown in FIG. 6, this motor has the structure whereina rotor R is eccentrically disposed within a housing H comprised of acasing 28 and a bracket 29 and rotatably supported by alubricant-containing bearing 32 and 33 disposed in the casing 28 and thebracket 29, respectively, through a rotor holder 30 and a shaft 31. Itshould be noted that since the eccentric rotor R is fixed to the shaft31, the position of the rotor R is determined by the shaft 31 which isflush with the housing H.

However, where the motor is of the above-described twin bearing type,the concentricity between the upper and the lower bearings becomesimportant. In the case of a coin type flat motor whose thickness isabout 3 mm, in order to prevent the tilting and blocking of the rotor,it becomes necessary to make the concentricity between the bracketfitting portion and each of the bearings as small as 10 μm or less, sothat each of the parts of the motor is required to have a high degree ofdimensional accuracy.

Such a problem ought to be solved by using only one of the bearings as acantilever type bearing, however, as will be understood from thethickness of the motor, the soft lubricant-containing bearing is notpractical in use because of the weakness of its fixing strength. Whenthe bearing fitting portion is elongated, the thickness of the motor cannot be reduced. When the thickness is forced to be reduced, in turn, thefitting allowance of the rotor holder fitted about the shaft becomesshort, resulting in another problem in the actual use thereof.

Further, there is also disclosed in JP-B-59-14966 (refer to FIG. 1) ashaft-fixed type vibrator motor in which the shaft is prevented fromprojecting outside its housing.

As maybe understood from its drawings, however, since both ends of theshaft are fixed to a bracket, it is difficult to assemble the rotor.That is, to explain the structure by using the reference numerals givenin the drawings, it is generally difficult to mount the rotor 12 to thebearings 5 and 6 respectively fitted in the brackets 2 and 3 through theshaft supporting brackets 10 and 11, because of the existence of thestator 7 as an obstacle. Further, the bearings 5 and 6 are not to bemounted to the shaft 4 but unavoidably mounted to the brackets 2 and 3for the purpose of facilitating the lead wire connection process. Thus,the outer diameter of the bracket is obliged to be made large, so thatthe sliding loss with respect to the shaft-supporting brackets 10 and 11becomes too large for the motor to be put in practical use. Unlike theshaft, the degree of roughness of the brackets 10 and 11 cannot be madesmall.

In this connection, in order to overcome the above-described variousproblems, the present inventors formerly proposed an invention disclosedin JP-B-6-81443 by taking notice of the fact that a vibrator motorhaving no output shaft which makes use of the vibration of its rotoritself is not required to rotate its shaft and that the shaft has onlyto be fixed at one end thereof. Thus, this motor has now been producedas a shaft-fixed type flat vibrator motor having no output shaft. Such amotor is now popular in the market due to the ease of assembly of therotor and the excellence of its cost performance.

With the recent trend of miniaturization of portable equipment, themotor to be mounted in the equipment is required to be more and moreminiaturized with minimum power consumption. If a motor with a shafthaving a diameter of about 0.6 mm (a shaft having a diameter of 1.2 mmmight be accepted) must be used, such a small-diameter shaft ofcantilever supporting type may require careful consideration to itsimpact resistance making the fixing portion of the shaft large, in turn,may affect adversely the reduction of the overall thickness of themotor.

The present invention has been made to overcome the above-describedproblems and an object of the invention is to provide a flat vibratormotor having no output shaft with a sufficient degree of impactresistant, using a small-diameter shaft, which can be assembled in asimple manner and which is thereby advantageous in view of manufacturingcost.

SUMMARY OF THE INVENTION

In a vibrator motor having no output shaft and constructed such that aneccentric rotor comprising a plurality of armature coils is disposedwithin a housing comprised of a casing and brackets, a commutator isdisposed on the rotor, brushes are brought into sliding contact with thecommutator, a magnet is caused to confront the rotor leaving a spacefrom the latter and a shaft supporting the rotor is prevented fromprojecting outside the housing, an improvement is made in such a mannerthat one end of the shaft is fixed to a portion of the housing, therotor is rotatably mounted on the shaft by assembling the rotor in thehousing from the other end of the shaft, the rotor is brought intosliding contact with the housing by urging the rotor forward or rearwardin the axial direction and the other end of the shaft is fitted into aconcave portion formed in the other portion of the housing therebypreventing the shaft from moving in the radial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an essential portion of a flat vibratormotor having no output shaft according to a first embodiment of thepresent invention especially when the motor has a coreless typeeccentric rotor;

FIG. 2 is a plan view of the eccentric rotor of the motor shown in FIG.1;

FIG. 3 is a sectional view of an essential portion of a firstmodification of the flat coreless vibrator motor shown in FIG. 1;

FIG. 4 is a sectional view of an essential portion of a secondmodification of the flat coreless vibrator motor shown in FIG. 1;

FIG. 5 is a sectional view of an essential portion of a flat vibratormotor according to a second embodiment of the present inventionespecially when the motor has a cored type eccentric rotor; and

FIG. 6 is a sectional view of an essential portion of a conventionalflat vibrator motor having no output shaft.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The first embodiment of the present invention is an application of theinvention to a flat coreless vibrator motor shown in FIG. 1 the motorincludes a thin stainless steel shaft 2 is fixed to the center of abracket 1 forming part of a housing H by pressure-fitting one end of theshaft into a holder 1a projecting inward as an integral part of thebracket 1 an eccentric rotor 3 is rotatably mounted on the shaft 2 fromthe open end of the shaft.

More concretely, the eccentric rotor 3 is constructed such that as shownin FIG. 2, three air-core armature coils 3a, 3b and 3c are arrangedeccentrically toward one side on the rear surface of a flat platecommutator 5 at an arrangement pitch of about 60°, and are made integralwith the commutator 5, which is provided with spark quenching elements4a, by a resin material 4 of a low friction factor. That is, the lowfriction factor resin itself serves as a bearing at the same time.Further, in the bracket 1 there is placed a ring-shaped magnet 6contains neodymium and which confronts the rotor 3 leaving a certainspace from the latter and inside a central opening of ring-shaped magnet6 there are embedded a pair of brushes 7 and 7 at a sliding open angleof 90° so that the brushes 7 and 7 are brought into sliding contact withthe flat plate commutator 5 with a suitable pressure contacting force.

On the other hand, a casing 8 which forms the other part of the housingincludes at its center a tapering through hole 8a into which the otherend of the above-described thin stainless steel shaft 2 is mounted. Theeccentric rotor 3 is brought into sliding contact with the casing 8 bythe pressure contacting force of the pair of brushes 7 and 7 by means ofa ridge 3d and a polyester film washer P disposed around the throughhole 8a. Consequently, the rotor 3 is constantly urged toward the casing8 and rotatably pressed against the polyester film washer P so thatthere is no fear of the rotor 3 moving toward the casing 8 to rubagainst it. The rotor 3 can be rotatably supported in a stabilizedmanner while always keeping a predetermined gap from the casing 8without varying the rotational position thereof.

Further, the ridge 3d is provided with a U-shaped or V-shaped groovewhich is concentric with the shaft 2 and which serves as a lubricantretaining means so that a lubricant such as grease can be maintained anda longer working life can be expected of the rotor.

The above-described assembling structure can be realized in a simplemanner in which the rotor 3 prepared in advance is fitted in the bracket1, also prepared in advance, from the open end of the shaft 2, thecasing 8 is placed over the bracket 1 and assembled with the bracket 1by caulking or welding the outer periphery of the bracket 1 to the openedge 8b of the casing 8.

Further, as a modification of the instant embodiment there is shown inFIG. 3 a coin battery type vibrator motor having a casing and a bracketserving as current feeding electrodes.

In this modification, a concave portion 88a of a casing 88 for receivingthe other end of the shaft 2 may be a resin material 88b having a goodsliding property and an insulating means 11a, such as polyethyleneterephthalate resin, may be outsert molded along the outer periphery ofa bracket 11 so that the concave portion 88a is insulated from thecasing 88 at the time of assembling the rotor. Further, in FIG. 3,reference symbol VV designates a V-shaped or U-shaped groove which isconcentric with the shaft 2 and which serves as a lubricant retainingmeans disposed on the side of the resin 88b of good sliding property,facing a portion of the low frictional factor resin 4 of the rotor 3.

In the instant embodiment, in order to make the casing and the bracketserve as current feeding electrodes, one of the brushes 77 is directlysoldered to the bracket 11 while the other brush 77 extends under themagnet 6 through a flexible plate F so as to be connected to the insideof the casing 88.

A further modification of the motor of FIG. 2 is shown in FIG. 4 inwhich the other end of the shaft 2 engages an adhesive polyester film P1in a through hole T in the casing 8.

Further, in order to form the concave portion for receiving the otherend of the shaft 2 for the insulating and sliding functions, the throughhole T is drilled through the casing 8 to receive the shaft 2 thethrough hole T has a diameter a little larger than that of the shaft 2so that the other end of the shaft 2 enters the through hole T by onehalf of the depth thereof and contacts the adhesive polyester film P1covering around the through hole T.

In the above case, it is desirable that the portion of the casing 8which surrounds the through hole T be recessed in such a manner that thethickness of the motor itself or the space provided in the casing is notsacrificed by the thickness of the adhesive polyester film P1 and thenthe film P1 be applied to the recessed portion.

By so doing, it is possible to obtain a structure capable of securingthe insulating and sliding properties of the rotor without sacrificingthe advantage of the motor being of small thickness. Accordingly, itgoes without saying that the structure can be applied also to theabove-described coin battery type motor.

FIG. 5 is a sectional view of an essential portion of a shallow coredtype flat vibrator motor having no output shaft according to a secondembodiment of the present invention wherein reference numeral 12designates a metallic dish-type casing with a bracket B fitted to anopen edge thereof. As in the case of the first embodiment, to thebracket B there is pressure-fixed a small-diameter shaft 2. Further, tothe shaft 2 a cored rotor 13, formed of two eccentric silicon steelplates K respectively bent outward at the outer peripheries thereof inopposite directions and an armature coil 13a wound around the plates, isrotatably mounted through a lubricant containing bearing J fittedinside. In addition, to the cored rotor 13, there is attached acylindrical commutator C having a sliding surface C with which a pair ofbrushes 77 and 78 are brought into sliding contact. The base portion ofeach of the brushes is embedded in the bracket B through a syntheticresin brush base 79. At the top of the dish-type casing 12 there isprovided a concave portion 12a which is formed by outsert-molding aresin material having a good sliding property so that when the rotor isassembled, the other end of the shaft 2 is supported by this concaveportion 12a.

Reference numeral 14 in FIG. 5 designates a cylindrical field magnetdisposed in the casing 12 leaving a space from the cored rotor 13 withthe magnetic center MC of the magnet being displaced from the center RCof the cored rotor 13 whereby the cored rotor 13 is always urged in thedirection of the displacement. Accordingly, since the cored rotor 13 isconstantly urged toward a slider 15, there is no fear of the rotorslipping off downward and the position of the rotor is stabilized.

Further, a core cover Ka made of a resin material may be extended inwardso that it may serve as a resin bearing in lieu of the above-describedlubricant containing bearing J.

By so doing, it becomes possible to bring the rotor into direct slidingcontact with the ceiling portion of the casing 12 through such a resinbearing.

As a modification of the above-described second embodiment of theinvention, it is, of course, possible to provide a battery type motor byeliminating the lead wires and terminals and causing the casing and thebracket to serve as electrodes, respectively. Further, one end of theshaft 2 may be fixed to the casing instead of the bracket.

Thus, even in the case of such embodiment, since the rotor lies at aposition to which the center of gravity of the rotor has moved, a largecentrifugal force generated at the time of rotation of the rotor so thatthe rotor acts as a vibrating motor.

As described above, according to the present invention, the rotor isrotatably mounted on the shaft from one end of the shaft whose other endis fixed to the housing, so that the rotor can be assembled from oneside of the shaft in a simple manner thereby facilitating automation,and since the radial movement of the shaft can be prevented withoutenlarging the fixing portion of the end of the shaft, even if thediameter of the shaft is small, the shaft can withstand an impact at thetime when the motor falls down, and the like. Further, since the rotorcan be urged forward or rearward in the axial direction, the variationof rotational position of the rotor can be prevented so that the rotorcan be rotatably supported in a stabilized manner without runningagainst any other structural member.

Further, if the rotor is brought into sliding contact with the housingby the pressure force of the brushes as a means of urging the rotor, therotor can be urged by only the spring pressure of the brushes so thatthe axial movement of the rotor can be controlled by a simple structureby making the effective use of the spring pressure of the brusheswithout increasing the number of parts.

Still further, in the case of the rotor, which is brought into slidingcontact with the housing by the magnetic force of the magnet, it ispossible to make the effective use of the attractive force between therotor and the magnet.

It should be noted that the present invention can be carried out in avariety of modes without departing from the technical idea orcharacteristics thereof. Accordingly, any of the above-describedembodiments is nothing but a mere illustration and should therefore benot interpreted limitatively. Further, the technical scope of thepresent invention is represented by the appended claims and is not boundby the text of the specification.

What is claimed is:
 1. A flat vibrator motor having no output shaft, themotor comprising:a housing comprising a casing and a bracket; aneccentric rotor having a plurality of armature coils and disposed in thehousing; a commutator attached to the rotor; a pair of brushes insliding contact with the commutator; a magnet confronting and spacedfrom the rotor; and a shaft having a first end fixed to a portion of thehousing, supporting the rotor, and a second end not projecting outsideof the housing and fitted in a concave portion of the bracket forpreventing radial movement of the shaft, wherein the eccentric rotor isrotatably mounted on the shaft, the eccentric rotor being brought intosliding contact with the housing when the shaft moves axially.
 2. Theflat vibrator motor having no output shaft as claimed in claim 1,wherein each of said brushes applies pressure to the commutator, urgingthe rotor toward the casing.
 3. The flat vibrator motor having no outputshaft as claimed in claim 2, including an insulating member having afavorable degree of slidability disposed at one of the ends of the shaftand the eccentric rotor slidingly contacts the insulating member.
 4. Theflat vibrator motor having no output shaft as claimed in claim 3,including lubricating agent retaining means disposed where the rotor isin sliding contact with the insulating member.
 5. The flat vibratormotor having no output shaft as claimed in claim 3, wherein lubricatingagent retaining means is disposed at each of portions where the pair ofbrushes are brought into sliding contact with the commutator.
 6. Theflat vibrator motor having no output shaft as claimed in claim 3,including lubricating agent retaining means comprising a grooveconcentric with the shaft and disposed on the rotor.
 7. The flatvibrator motor having no output shaft as claimed in claim 3, includinglubricating agent retaining means comprising a groove concentric withthe shaft and disposed on the housing.
 8. The flat vibrator motor havingno output shaft as claimed in claim 2, including lubricating agentretaining means comprising a groove concentric with the shaft anddisposed on the rotor.
 9. The flat vibrator motor having no output shaftas claimed in claim 2, including lubricating agent retaining meanscomprising a groove concentric with the shaft and disposed on thehousing.
 10. The flat vibrator motor having no output shaft as claimedin claim 1, including an insulating member having a favorable degree ofslidability disposed at one of the ends of the shaft and wherein theeccentric rotor slidingly contacts the insulating member.
 11. The flatvibrator motor having no output shaft as claimed in claim 10, includinglubricating agent retaining means disposed where the rotor is in slidingcontact with insulating member.
 12. The flat vibrator motor having nooutput shaft as claimed in claim 10, wherein lubricating agent retainingmeans is disposed at each of portions where the pair of brushes arebrought into sliding contact with the commutator.
 13. The flat vibratormotor having no output shaft as claimed in claim 10, includinglubricating agent retaining means comprising a groove concentric withthe shaft and disposed on the rotor.
 14. The flat vibrator motor havingno output shaft as claimed in claim 10, including lubricating agentretaining means comprising a groove concentric with the shaft anddisposed on the housing.
 15. The flat vibrator motor having no outputshaft as claimed in claim 1, including lubricating agent retaining meanscomprising a groove concentric with the shaft and disposed on the rotor.16. The flat vibrator motor having no output shaft as claimed in claim1, including lubricating agent retaining means comprising a grooveconcentric with the shaft and disposed on the housing.